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False eyespots may help the eyed click beetle look scary to predators.

This week while meandering along a pathway in a forest, Bug of the Week happened upon a most remarkable beetle, the eyed click beetle. One look at this big beauty (up to 1 ½ inches long) provides instant understanding of how “eyed” became part of its name. As you stare at the beetle, two large and impressive eyes stare back at you. But these are not true eyes! The real eyes are rather small and are located on the head of the click beetle near the base of the antennae. The markings on the back of the beetle are false eyespots like those we have seen on other guests of Bug of the Week, like the Polyphemus moth, Antheraea polyphemus, swallowtail larvae, Papilio sp., and Owl butterflies, Caligo sp.. The eyespots are thought to startle or confuse predators such as birds or reptiles that might want to make a meal of a tasty beetle.

The spine and notch are part of the engineering that give this beetle its click.

Ok, that explains the business about the “eyed”, but what about the click? To understand the click, you must be lucky enough to find and capture a click beetle. When grasped by a predator like a bird or a geeky entomologist, the eyed click beetle produces an unnerving snap of its body so forceful that it can be flung from the grasp of its tormentor. How do they do this? Click beetles have a remarkable spine on the under surface of the first segment of the thorax. This spine fits into a notch on the second thoracic body segment between the legs. The beetle flexes its body in such a way that the spine quickly releases with an audible click. When placed on its back, this snap can catapult the beetle an inch or more in the air! The beetle often lands right side up, but if it doesn't the process may be repeated until the beetle finally rights itself. The eyed click beetle is also known as the eyed elater, a name coined from the Greek word for 'that which drives, hurls, or sets in motion' – it’s pretty obvious how they came by that name. Smaller, less dramatic click beetles are frequent visitors to our porch lamps in spring and summer.

The larva of the eyed elater has powerful jaws to kill its prey.

Larvae of several species of click beetles are plant eaters and when they feed on subterranean parts of crops such as the roots of wheat, corn, or potatoes, they can be noxious pests. Many click beetle larvae, including the eyed click beetle, are meat eaters rather than plant eaters. The fierce larvae of the eyed click beetle have powerful jaws used to disable and dismember victims. Prey commonly includes other insects such as larvae of flies, caterpillars, and other beetles, such as bess beetles.

Click beetles are great fun to capture and most entertaining, but please put them back unharmed when you are done.

References

Bug of the Week thanks Paula and Bonnie, who were the inspirations for this episode.

For more information on click beetles and their kin, please visit the following web sites: